1. Field of the Invention
This invention relates to security for data objects; more particularly, the present invention relates to improved security based on subliminal and supraliminal channels for data objects.
2. Description of Related Art
Digital watermarking enables a number of security features in handling various data. Application of a cryptographic protocol to the limits of steganographic measures of perceptibility (i.e., embedding a digital watermark just shy of the point where the watermark becomes humanly perceptible) yields both robust and secure techniques. Digital watermarking serves to tamperproof data by maximizing the encoding level of the subliminally embedded data, a form of information hiding, while preserving the fidelity of the cover channel (as represented by a digitally sampled signal stream). When attempts to remove or erase a digital watermark should result in perceptible changes to the cover signal, such watermarking serves as a simple form of perceptible authentication. Moreover, such watermarking preserves the signal's commercial integrity because to remove the watermark necessarily degrades the signal quality, resulting in a lower commercial value of the data, assuming that the quality of the signal plays some role in determinations of that value. Authentication and verification of the watermarked signal are functions of the predetermined quality of the cover signal as intended by the sender of the watermarked data.